Son, you're making my head hurt! Glad there are smart peeps out there to figure this stuff out; appreciate you're showing the process!

You're the one giving me wisdom. I like your deduction that your NanoVA wasn't providing sufficient current for inductive coupling. 73, KF0NNQ.

Looking foward to the revisit of this after testing

Well it might have to get a field test

Impedence matching. When matched you have maximum energy transfer. Look at the impedence on the VNA, and not so much the SWR. The transformer-cap--reactors--are the transmission between the radio engine and the rear wheels antenna. Get a thermal camera and "see" where the RF power gets used up-hot cores- indicate poor matching and or improper core material composition.

Looking forward to what you find. Cool design.

It's all about the pronunciation. 😂 (Now all kidding aside...compare the image at 9:20 with the schematic of the Johnson Matchbox, and you'll see why this is the CORRECT placement of the capacitor.) Nye Viking knew exactly what they were doing. This is also why it is important to fact check designs against proven ones from decades ago. I can't tell you how many times I've seen schematics copied incorrectly and used that way in publication after publication. Always "trust but verify". PS, this UNUN can also be modeled in SimSmith for those who wish to take it to the next level. 73

Snow blowing will have to wait for now. Time to go the bench and slap on some caps on the secondary’s and have some fun. Thanks ape for the fun and practical videos.

It will be interesting to see the test under load results. I had forgotten about AA5TB's site. Lots of good information there!

hi sotabeams used to do one with veriable cap for qrp and you just tune to loudest on rx and it was 1:1 using 40m tx wire and 5m counterpoised elevated to 1m off the ground and the first time i used this was after a thunderstorm with inverted using a 10m mast in the middle and i worked japan from uk on 5watts so very lucky and the ease of changing band u just turned the cap and away u go very simple worth making M0DSY

That is some fine material to digest. I think you are correct that you are not getting enough current through the system for the coupling to take place. I would think with the capacitor across the secondary it should bring the high bands closer in VSWR to the lower bands. Really cool discussion. This is why the CaRH folks and their best teaching channels out there. Bravo

You're such a great buddy, buddy!

That twisted primary is where they get you!

NanoVNA output power is somewhere around -9dBm. The bigger commercial benchtop units are around 0-15 dBm. You might need to step up to one of the big boys now 😜

I’m looking at making my first efhw. Maybe 4 turns primary to get induction to work. I’m digging the double core 4:1 balun. Very quiet on loop. Still have to test on 66 ft OCFD. Thanks as always. I’m Leary of capacitors.

The one not connected is just galvanically isolated which does have the benefit of lower noise.

This is what I call an "isolation transformer", you get extreme amounts of common mode rejection. I use 5 turns : 5 turns to couple signals into my SDR this way, it is very lossy but can do good things for your receive. This transformer is similar to the LoG antenna transformer. I'll build one of these up and post the results on discord.

That looks a bit like the unun design that is described by the guys at ocfmasters as well... I've built one and just haven't got it hung up yet to test 😁

Yes I played with this type of windings. It seemed to tune up very easily 80 -10m with some very low swr in the right places but would get fairly warm at just 50 watts

Interesting and informative on the detail you guys put into your products. MM0OPX has a good design, and I’m keen to try your one. Bit of an antenna farm going on around my property now.

That a great idea to test. so far i have not wound that way. I would say make it as a antenna and check SWR at 1/2 watt or so. ICOM 705 will plot a SWR graph. what I have done and it works great is no cross over on secondary winding. ant lead will come out near the input. that still tunes fine with the 100 PF cap on input. the cross over half way is so ant lead comes out opposite of the input. also the twisting does not matter on primary . in fact you do not need that at all. do first 2 wraps run the tap .then continue 14 turns . cross over if you want. the tap is the ground . the 2 turn wire wrap is input and end of 14 turns is ant. that works and tunes the same. but your first prototype buy twisting the first 2 turns and cross over at 8 is the easiest and best for winder base you are using. I did a 2 stack of FT 240 type 61 . 49:1 with 3 KV 100 PF cap. made of 10 AWG solid mag wire. using 2/14 turns . tunes great 10/11/12 meters adjusting wire a few in. I put different color heat shrink for 3 bands. up a DX commander 10 meter pole and counter poise and choke on coax at antenna. 1.3 SWR or better . and ran 500 watt FT8 on 10 meters. 2 stack of T240-61 stay cool. my tube amp wont do 500 watt FT8 long so was a short test. but 250 watts ran hours no heating. same thing done with type 43 mix. got some heating and slight higher SWR . still under 1.5 :1 . found type 61 on 10 meters runs tad better. I can say the 31 mix gave bad SWR . on 10 meters. never even tried on air. that meant for common mode choke. I have a thermal imaging camera as part of my work as a electrician . when using smaller AWG wire I can watch the wire heat up before the toroid. when the wire is heavy like 10 AWG the wire stays cool then after a wile the ferrite ring starts to heat up. neat to watch. 73's

I have built several of the efhw antennas without adding a capacitor (there is probably some inevitable capacitance created by wraps of the coils). It doesn't seem to make a lot of difference from what I've seen. Thanks for sharing! 73- AA4K

Just some thoughts from my understanding. The capacitor has been added to bring the higher frequency Swr sweet spots into the ham bands. One advantage of a dc ground when the primary and secondary are connected is for high voltage protection before the coax enters the shack. A side note I heard is that capacitors tend to fail shorted. I think it was a power supply repair video. It was an argument to use two capacitors in series. If one shorts you don’t get a short across your coax line. Thanks for sharing your thoughts on the EFHW.

Great topic. Hallelujah, where's the Tylenol

It might be interesting to see what the Fr is with the 100pf cap on the secondary vs what the Fr is with the cap across the primary winding with two and three wraps. IDK, i'm just wondering. Then if that leads to nothing, connecting it to antenna to see how it deals with the reactance and resistance presented by the antenna. At what F does the circuit go to parallel resonance, infinite Z? There seems to be mixed reports between using shunt caps and not....

Hi Ape, just wondering if I could either get, or purchase one of the wire winders ??? It appears that your’s are of a higher quantity then I can find in VK land. Let me know, thanks for all the knowledge that you, Steve,Jeem and Chuck have given us and keep giving us. David Wilson (VK2AAW)

Fuchin good video.

I always thought the reason to put the C on the primary side used to be the voltage rating: Let’s say TX with 100W / 200Vpp and multiply that by your transformer ratio of 49 or 64 and the capacitor on the secondary side has to be able to deal with that. - Maybe that’s not an issue anymore these days, but maybe high quality 10-15KV capacitors were hard to come by in the early days. The opposite is also true: Better put a high quality C with lower (yet still sufficient) voltage rating on the primary, than your cheap Aliexpress 3KV variant of dubious origin. Please correct me when I am wrong: I usually am! 😜

Great content! The next great antenna hasn't been invented yet!!! Sometimes I wonder how many antennas were mistakes...🤔

Fight the Good Fight!

I’m sure you have seen Colin and using 2 transformers back to back. Then do a through test S1 to S2 and divide the results by 2 for loss. Give it a try.

I don't think it's an output power issue of the nanoVNA, but you may be right. Have you tried using a longer transmission line between the nanoVNA and the transformer? Transmission line length can play its part in reflections. I'd be interested to see what the sweep looks like for a 5m long and/or a 10m long transmission line between the nanoVNA and the transformer. Also, I'd try more primary windings if you can, while still maintaining your desired ratio. That would also be another good test, in my humble opinion.

Hey Ape, As I’ve said before You have way more experience with ferrite Xfmrs than I do, but from the research I’ve been doing the Cap across the Xfmr’s input is to minimize loss (not for SWR purposes) at higher frequencies, like on 10 meters. Also loss wise the testing I’ve seen prefers the Fair Rite 2643251002 core (43 mix, which is thicker for its diameter) and close wound in autoformer type windings tapped (not twisted) at 2 turns with 14-15 turns total for 49-56:1 ratio with a 120pf TDK cap IIRC (it would be interesting to see if your primary/ secondary configuration follows suit AND minimized CMC). It seems this geometry, and tight windings seriously helps to reduce losses and will easily handle 100 watts without overheating. And, Yes, the TDK caps are preferred for minimal losses... SEE: End Fed Half Wave Transformers.......Are they as good as we think? - MM0OPX Field Radio Best Ferrite Core For a 100w End Fed Half Wave Antenna - MM0OPX Field Radio for a good videos on this. Another is… Trash that FT140-43! EFHW xfmr geometry STILL matters! - Evil Lair Electronics Seem to be the (or one of) originator of this concept, BUT you need to ignore his jibes at others he feels slighted him. There are more videos that have tested this design (back to back xfmrs, and calculated) for efficiency, that back up these results. Also from the circuits I’ve seen, putting a Variable Cap across the output coil is so you can Tune the impedance match from/to the antenna, and is a Variable Cap so it can be tweaked as you change frequencies / Bands. There’s Random Wire antennas fed in similar ways in various publications, usually not with coupling coils. More than one way to Skin a cat! Keep On Keepin On! 73 mike

interesting video

I can't provide any feedback besides great video on an interesting topic

I still wonder why we spend so much time on the transmit side of the equation. I wonder what happens when you release the PTT and start listening? In some of these antenna designs, where we are transforming, what does that transformation do to signals coming to our receiver. Especially weak ones.

Only thing I can think of is maybe try getting the primary winding closer to the secondary winding. Might help the NanoVNA. Also how is the efficiency compared to the typical design? Might not matter for QRO but might make a difference for QRP. Just curious and thanks for the video

The capacitor only comes into play when you connect a resonant load (the antenna). From my experience it lowers the SWR and changes the bandwidth (not the frequency) on the 10m portion of a 4010 EFHW. You need to front load the antenna to bring the 10m dip down in frequency if it doesn’t fall where you want it. The cap (80-120pF) is to lower the SWR. The NanoVNA puts out close to -10dBm to +1dBm which is ample voltage at 50ohms to test toroids and transformers. Receiver front ends work at -120dBm with toroid wound filters, do they not? When testing transformers it’s better to connect two devices back to back. Connecting an assumed impedance substitute (a resistor) is far from ideal. A right royal pain in the butt as you need to wind two of each. I’ve lost count of how many toroids I’ve wound and tested for EFHW use but I’ve settled on a galvanically isolated design similar to yours. Coil shortened antenna to reduce the 40m portion length and tunable from CW to Phone on the fly for 40m and 20m. I get at least 1Mhz of BW (VWSR 2:1) at 10m so no tuning is not an issue. I get a full 200KHz (7.0-7.2 in Japan) on 40m with the dip tuned to the middle. A good 3 years into this build though 🫠 73 John

Talking seriously, magnetics is a weird topic. You suspect there is not enough current/excitation on the nanovna, but it might not be the case. There is a guy in VK land, Owen Duffy, which tries to explain the physics of those high rate transformers, and seems to have a nice technical background on the topic. Unfortunately, his explanations lack a lot of details and I cannot grasp 30% of his claims. One of the points he makes is about leakage inductance and parasitic capacitances, which he can model and measure very easily with a vna. I got to reproduce some of his experiments but I don't understand what I can change to improve it. Anyway the one take away I got from his blog is that the capacitor on the secondary intends to create a resonance on a specific band, while the capacitor on the primary counteracts the leakage inductance and makes the transformer more flat. If you add a capacitor to the primary and the swr goes up, it might be too much or too little capacitance compared to the leakage inductance. I should have paid more attention to my electromagnetics classes...

As an electrician it make sense!!!

Maybe try and get the green wire wound as tight as the magnet wire. Maybe try with magnet wire instead.

Hi there I was wondering if you could help me with my computer problem? Well configuring my RTLSDR version four into my dell all in one windows 10 computer, I messed up. Apparently I goofed up the Zadig and now I cannot even login to my computer as my wireless mouse and wireless keyboard are no longer recognized, do you have any ideas? Thank you so much.

If the Nano VNA milliwatt output is not enough to magnetize that large core... how could receive possibly work through that core at a fraction of a microwatt level signals? Think about it. 🤔🤨

Hi Ape -- have you taken a look at Model 36130 - 36:1 for EFHW, 150 from Balun Designs? When I saw the loosely coupled transformer (poor description, but you get the idea) on the livestream, my mind immediately went to this one. Unlike the wrap around the iron core you were talking about, this is a broadband approach. But seems to require a few more tricks w.r.t. the radiating element and the counterpoise, to bring it in. It does look promising in terms of efficiency, though. From the webpage: ""After much research and testing, a new transformer design for End Fed Half Wave (EFHW) antennas has been achieved. Developed by Bob Glorioso, W1lS and Bob Rose KC1DSQ, they discovered that most transformers for EFHW antennas used higher impedance transformations than necessary and were wound in a way that limits the high frequency response of the transformer."" .. I seem to recall that Waters and Stanton may have talked around this design a little bit, but I don't know if it was attributed to W1IS and KC1DSQ. I thought I found an article on this design, but I dont immediately see it in my files to give you the title.

Crazy stuff here SA. The cap will have about an Xc of 450 ohms at 80m and half that at 40m. You are sticking that mf (micro farad) on the output where ideally, it's what, 1800 ohms if it's a 36:1 or much higher if it's a 49:1 or some such. Have you ever heard of a path of least resistance, son? What the farad? Is there less noise? Of course there's less noise. The antenna is shorted out. Episodes before, I have asked you about XL values. I don't know if you found anything out or not but you need relatively high XL values looking into the input with that transmission line unloaded on the output, otherwise you are just shorting out your signals before they come close to the antenna. If you want to make a balun for one specific frequency, a cap can work out well like this by making it a tuned parallel tank circuit. Your jX value can skyrocket which is actually a good thing in this portion of the design because we're not talking about the jX of the antenna which we want to keep near zero. But face facts. You're trying to build a multi band antenna and that's hardly a single frequency antenna. This makes my head hurt. I want back on my school bus with unruly children. I can fill out reports on them.

MOTO, but if you're not seeing a change in the SWR sweep with/without the cap [on the primary]....there's something else wrong. I've made nearly a dozen EFHW UNUN's and every one exhibited change when adding the cap.

I got nuffin, I'd have to refer to my AARL Antenna book. Lol I still have to build my Apollo, so do some moe testin' son.😄👌

Not sure how my experience as an automation engineer would apply, it seems the way your wraps are laid out is not conducive to the inductance needed. I'm not an RF guy, so maybe I'm missing something here. Ferrites in my application are used to null transients and give a smoother response.

Different size resistor?

Much more simple design...Maybe your on to something!

Ah yes, the "Fuchs" Antenna. I totally won't reuse that immaturely.

Make Jeem go outside to test it, LOL

You make me question reality sometimes....

Dear Mr Ape, Could you please suggest a reliable source for good quality Nano VNA's these days? Or similar pocket size VNA devices with PC support for downloading and analysis of data, preferably using Linux software. There's a veritable jungle of shady Amazon vendors pushing crappy clones of clones of clones with questionable quality to say the least. Definitely monkey business! 🙈🙈🙈

Please pronounce "Fuchs-" like the "u" in "footage" and the "ch" in "fox". 😂

This guy uses the coupling idea in this video kzfaq.info/get/bejne/aK-hi5Oo3qu8lok.html

Why use a vulgar expletive as click bait? Unsubscribing ...

👍Thank you sir . sir your mail id please.